Examples of X-ray imaging equipment to take a fluoroscopic X-ray image of a subject includes one having an X-ray source that emits X-ray beams in a cone shape and a flat panel detecting element (abbreviated as “FPD”) that detects them. The FPD has an X-ray detection surface where the X-ray detecting elements are arranged in two dimensions.
X-rays emitted from the X-ray source are once scattered in the subject, and then enter into the FPD. The scattered X-rays entering into the FPD lead to a lower contrast fluoroscopic X-ray image. To avoid incidence of such the scattered X-rays into the FPD, a sheet-like X-ray grid having strip metallic foils arranged therein is provided in the X-ray imaging equipment so as to cover the X-ray detection surface of the FPD.
Typically, an arrangement pitch of the detecting elements in the FPD is not identical to an arrangement pitch of the metallic foils in the X-ray grid. Consequently, a moiré occurring from interference between the both pitches appears in the fluoroscopic X-ray image. Thus, in order to remove the moiré, the conventional X-ray imaging equipment performs image reconstruction by conducting frequency analysis of an image and removing frequency components of the moiré.
The detecting elements may occur on the detection surface of the FPD that fail to detect X-rays due to defects in a semiconductor device. Such defect sometimes occurs from failure in a gate drive or a read-out transistor, and thus all the detecting elements arranged in series are unable to perform detection. As a result, a straight line having aligned white or black defective pixels appears in the fluoroscopic X-ray image. When the foregoing calculation for removing the moiré is performed to the fluoroscopic X-ray image having such straight line, the defective pixels cause disturbance in regularity of the moiré pattern. In the image after the calculation, there appear the straight line having arranged defective pixels and a ghost with the straight line exuding and spreading in a moiré arrangement direction. As a result, visibility of the fluoroscopic X-ray image is to be degraded.
Methods of processing images that are intended to solve such problems include a method of complementing defective pixels in advance, which is disclosed, for example, in Patent Literature 1. Specifically, in the conventional image processing method, as shown in FIG. 10(a), a defective region L is complemented with reference to a pixel value of the pixels adjacent to the defective region L. In addition, when the defective range L is arranged in a direction where a dark range region D in the moiré extends, a moiré that must have appeared in the defective region L deviates from and the moiré that appears in the pixels adjacent to this. Consequently, an approach shown in FIG. 10(a) cannot be adopted. Alternatively, as shown in FIG. 10(b), a statistical process is performed from right and left pixels E1 and E2 to the regions adjacent to the defective pixels a to be complemented that are arranged in series in the mere arrangement direction (x-direction), for calculating the most proper pixel value and substituting the value into the defective region L.
[Patent Literature 1]    Japanese Patent Publication No. 2002-330341